Decreased Use In Skeletal Muscle

Question 1

Decreased Use of Muscle Results in…

Answer 1

Decreased muscle mass > Decreased strength
Anti-gravity muscles degrade faster
Type 1 fibers begin turning to Type 2
Decreased endurance, oxidative enzymes, and local blood flow
Edema

Question 2

Bed rest/Unloading Intervention

Answer 2

Exercise (can be done in bed rest)
Blood flow restriction
Nutrition (protein, amino acids)
Pharmacology

• Effects of decreased use are reversible and to
  some extent may be preventable*

Question 3

Immobilization in a Shortened Position

Answer 3

Loss of sarcomeres (25–40% loss)

Atrophy is much greater when immobilized

Question 4

Immobilization in an Elongated Position

Answer 4

Sarcomeres added and overall fiber length increases

Positive adaptations appear to be due to IGF (due to stretch)

Stretch weakness (slack due to lengthened adaptations)

Question 5

Intervention Summary

Answer 5

Muscle’s position during fixation

E-stim and resistance training during immobilization may help to attenuate atrophy

Rehabilitation of both range and strength to optimize return of muscle function

Deal with activation issues earlier in rehab

Cross education

Muscle vibration

Takes 2–3x longer to restore than it does to lose